The primary objective of this study is to investigate the role of cytokines, autocoids and other vascular derived substances in the pathogenesis of preeclampsia. TNF-alpha, fibronectin, endothelin and platelet activating factor (PAF) will be evaluated longitudinally in plasma, sera and amniotic fluid for their possible application in detecting patients at risk for preeclampsia. Levels of protein and gene expression via in situ hybridization and immunodetection for TNF- alpha,TNF receptor, fibronectin, fibronectin receptor, endothelin and PAF will be evaluated in placentas, uterine biopsies and umbilical cord derived endothelial cell monolayers. Blood from pregnant patients who are diagnosed with preeclampsia will be obtained from specimens originally collected for SPID # 733. Use of the GCRC designed data base and statistical analysis will be done as mentioned in SPID #733. The Core laboratory will be utilized for blood separation and laminar flow hoods.